The ecological conditions for growing strawberries, as far as the climate is concerned, are that strawberries can be grown in very different ecological environments, from the subtropics to the temperate continental climate to the southern border of the Arctic. In our region, climatic factors are more important than soil factors for successful strawberry cultivation.
Temperature, water and humidity, light and wind are important climatic factors for strawberries.
Temperature
Along with the distribution of precipitation during the growing season, minimum temperatures are the most important factor to consider when choosing an area for strawberry cultivation.
It is known that the genotype of the strawberry species and variety, as well as air and soil temperature, directly affect the metabolism and the life and annual cycle of the plant.
Regardless of the fact that strawberries can thrive in wide temperature ranges, it is possible to observe significant differences between different species and cultivars, different ages and physiological states of the plant, different organs and phenophases in the strawberry’s annual cycle. This is confirmed by the fact that the garden strawberry is significantly more sensitive to low and very high temperatures than its parents, the Virginia and Chilean strawberries.
The optimal temperature for growing strawberries is from 20 to 25 °C in a moderately continental climate.
Low temperatures during the winter actually rarely damage the plant because the strawberry tolerates short-term frosts of -35 to -40 ºC when it is under a thick snow cover. The greatest damage occurs when frost occurs during the winter, then the plant dies at -15 to -18 °C, and especially if the seedlings were planted late in autumn, because they cannot take root well until winter.
Also, late spring and early autumn frosts have a significant impact. If strawberry seedlings are planted in autumn, areas should be chosen where the occurrence of early autumn frosts is rare. After a period of warm weather, the strawberry plant may die in the spring at -5 to -7 °C. Late spring frosts, at a temperature of -2 °C, cause damage more often, especially during flowering and on newly planted fruits, which are even more sensitive than flowers because they freeze at -1 °C. The strawberry root is also sensitive to frost and begins to freeze at -8 °C. Older strawberry leaves are not resistant to frost, while young leaves are resistant and overwinter successfully.
The growth of aerial organs begins at a temperature of 2 to 8 °C, and the growth of roots at 7 to 8 °C. Fruits grow and ripen quickly at daily air temperatures higher than 16 °C, and the most lush growth of strawberry rosettes and the formation of boils is at daily temperatures of 23 °C.
In addition to low, high temperatures can have a harmful effect, especially during flowering and seeding, development, ripening and harvesting of fruits. The harmful effect is not reflected directly on the plants, but indirectly through a more intensive reduction of soil and air moisture. Harmful consequences are more pronounced on less suitable soils for growing strawberries, such as sandy, gravelly and heavy clay soils, while they are not so important on soils with a lot of humus. This limiting factor is removed by regular tillage and irrigation of plantations.
Light
Sunlight is a direct source of energy for many processes in the strawberry plant, such as the process of photosynthesis. For the processes of respiration, transpiration, absorption, biosynthesis of proteins and organic acids, light is a source of heat, and it also acts as a stimulus for growth, development and reproduction. Sunlight affects its quality, composition and wavelength, strength, intensity and duration during the day and night.
White sunlight with a wavelength of 390 to 760 nm is necessary for the process of photosynthesis, while ultraviolet radiation is harmful to the plant, and infrared radiation provides warmth to the plant.
In areas with a large number of sunny days and cool nights, the garden strawberry thrives best and produces quality fruits, because in such conditions a large amount of assimilates is created, while the losses in the process of respiration during the night are small.
The length of the day and the photoperiod play a significant role in the process of the formation of heather and flower buds. Thus, the homogeneous varieties, which are the most represented in intensive strawberry plantations, are short-day plants, so the differentiation of flower buds begins from mid-September to the end of October, when the day lasts from 11 to 13 hours.
As the length of the day increases from the equator (12 hours) towards the poles, it follows that the varieties of the southern regions do better in short day conditions, while the northern varieties in long day conditions.
Water and humidity
During the growing season, the amount and distribution of rainfall and the humidity of the air and soil have a great influence on the yield.
Since the strawberry is a herbaceous plant characterized by a large leaf surface and a shallow root system, it needs large amounts of water for normal growth and fruiting during the entire growing season, especially during the fruit ripening period in May and June. Therefore, it is recommended to plant strawberries in soil that contains 75 to 80% of its full water capacity.
The lack and excess of water in the soil has an unfavorable influence on the life functions of the strawberry, which later adversely affects the yield and quality of the fruits.
The lack of water has a harmful effect on the strawberry so that the root system is poorly developed in the surface layer of the soil, the plant’s vigor decreases, flowering lasts shorter, fertilization is worse, the fruit yield decreases, the fruits are smaller, ripen earlier and are of poorer quality, and the formation slows down heather and flower buds. Also, the number of generations of new leaves depends on soil moisture. During droughts, two to three generations of leaves are formed, and with optimal soil moisture, four generations.
Areas with higher relative air humidity during summer are suitable for growing strawberries in general, while in areas with low air humidity in summer, early varieties can thrive because the heat period will occur after harvest. Thus, very early and early varieties of strawberries will suffer less from drought than late varieties.
Soil moisture is also important. Only soils rich in humus manage water best, so they will be used for the safe cultivation of strawberries.
Water quality is also very important. Laboratory tests of water quality should show low amounts of sodium, chlorine and boron. Galletta and Himelrick (1990) state that if the irrigation water contains more than 700 to 900 ppm of total salts, special care is needed in the application of such water to prevent the accumulation of salts to toxic concentrations.
Wind
It is most often considered an unfavorable ecological factor in the cultivation of strawberries for several reasons. One reason is that it dries out the soil and air and thereby increases evaporation and transpiration, during flowering it causes drying of the pistil nose and thus reduces the intensity of fertilization, interferes with the flight of bees and thus fertilization, makes protective spraying of strawberries difficult and increases the effect of downy mildew. Therefore, it is not desirable to plant strawberries in windy positions, but if the plants are already planted, it is necessary to install windbreaks.
In addition to the negative impact, a gentle breeze can also be beneficial because it improves air circulation and thus ventilates the above-ground parts of the plant, making it difficult for pathogenic fungi and other diseases to develop.
Of the soil factors, the most important is the soil, on which the yield itself depends to a large extent.
Soil
Garden strawberries can be grown on all types of soil, but with higher i.e. lower yield and quality. This allows it to have a vascular root that develops mainly in the surface layer of the soil, at a depth of about 15 cm.
Strawberries achieve higher yields on loamy-sandy soil, chernozem type, on soil that is structural, moderately deep (50 cm), drained, fertile with 3 to 5% humus, slightly acidic to neutral reaction, pH 5.5 to 7.5 and well supplied with water. Loamy-sandy soils contain 50% of dust and clay and 50% of total sand. Therefore, they have a favorable water-air relationship and thermal regime and are easy to process. Soils containing more than 60% dust and clay or more than 60% sand are not good for intensive strawberry cultivation. Clay soils, because they are too heavy, retain water for a long time, have a poor water-air relationship, are cold and difficult to cultivate, while sandy soils poorly retain water, which is quickly washed away, and with it all nutrients, so the plant soon becomes “hungry”. Strawberries do not tolerate alkaline and carbonate soils very well, as they suffer from ferrochlorosis (yellowing) on them.
Furthermore, the soil must be free of weeds because, in addition to depriving the strawberries of nutrients and water, they shade the plants and thereby promote the spread of infections, diseases and pests.
The most important orographic factors are altitude, terrain slope and exposure.
Elevation
When choosing a location, it is necessary to take into account local conditions.
Garden strawberries are successfully grown up to 700 m above sea level. By increasing the altitude, the temperature of the air decreases and the vegetation period of the strawberry is shortened. Strawberries can be grown at a slightly higher altitude of 700 meters on slightly inclined, southern positions that are sheltered from strong and cold winds.
Slope of the terrain
As for the slope of the terrain, strawberry grows well on gentle slopes, from 2 to 5 degrees. On such slopes, there is no retention of excess moisture and cold air, while erosion is reduced to a minimum. It is considered that it is not justified to grow strawberries on terrain with a slope of more than 8 degrees.
Exposure
Exposure affects the lighting, temperature and humidity of the place, and thus the movement of vegetation and the ripening of fruits. It is known that strawberries ripen 10 days earlier in southern locations than in northern locations because they are warmer and receive more sunlight. Since the drought is more intense on southern, southeastern and southwestern exposures, only early varieties are considered for cultivation. Mid-late and late varieties should be grown on northern slopes where the impact of summer drought is mitigated. Mid-early varieties do well on north-east and north-west slopes. In flat terrain, the choice of varieties is easier, and it depends on the climate of a certain area.
Closed valleys where cold air is trapped should be avoided.
